Concentration of aqueous alkene halohydrin solutions



Janyza, 1940.

W. C. B. SMITHUYSEN CONCENTRATION OF AQUEOUS ALKENE HALOHYDRIN SOLUTIONSFiled oct'. 25, 19:57

Patented Jan. 23, 1940 UNITED STATES PATEN T -OFFICE CONCENTRATION OFAQUEOUS AHALOI-IYDRIN SOLU'1 IONS` ment Company, San poration ofDelaware Francisco, Calif., a cor- Application October 25, 1937, SerialNo. 170,840 In` the Netherlands November 17, 1936 9 Claims.

The present invention relates to the manufacture of halohydrins and moreparticularly to the manufacture of ethylene chlorhydrin.

The object of the invention is to provide a method whereby aqueoussolutionsof halohydrin containing a greater concentration of halohydrinthan the respective halohydrin-water azeotropic mixture may be producedin a more economical manner. y

This is accomplished, according to the present invention, by executingthe process continuously in a certain prescribed manner and in such acombination of steps as to result in a method 4affording substantialheat economies.

Halohydrins may be prepared according to any one of several schemes,such as the raction of a glycol with a hydrogen halide, an oleine with ahypohalous acid, an allyl type alcohol with a halogen or an olefineoxide with a hydrogen halide. Due to the abundance of olefinehydrocarbons, the method wherein an olene is reacted with a hypohalousacid is by far the most important from a commercial standpoint. In thismethod, however, the h lohydrin must be recovered from a dilute aq eoussolution contain-A ing hydrogen halide. Due to the particular physicalcharacter of the lower halohydrins, especially the most importantmember, ethylene chlorhydrin, their recovery from such dilute solutionsand the concentration of such solutions have provento be very expensiveoperations, costing more in fact than the raw materials.

Halohydrin solutions of desirable concentration are made, according tothe present invention. by

a two step continuous process using the principle of azeotropicdistillation. In the first step, a partial concentration is accomplishedby a fractionstion of the dilute solution, and vin the second step thepartially concentrated material vis concen- I 40 tratedA to the desireddegree by a fractionation in the presence of an'entraining agent.

I have found that very decided economies may be realized when theoperations are executed in a continuous manner'. This is not only due tothe normal advantages of continuous operation over batch operation, butis also due to the fact that by operating continuously. certainconditions may -be maintained to give decided heat economies.

While it is the custom to neutralize the free acid before attempting theconcentration, I have found it more desirable to operate with the acidVsolution, i. e., without iirst neutralizing the free halogen acid. Theelimination of the neutralizing step has three advantages, to wit: (1)the cost of the neutralizing agentis eliminated, (2)

the free halogen acid may be recovered, (3) less halohydrin is saponiedduring the concentration with a consequent better yield. With respect tothe first advantage, it should be noted that while the cost of a certainfew neutralizing 5 agents, such as marble chips, is very slight, thesalts resulting from the neutralization are quite detrimental. I havefound that in the presence of CaClz, for example, the yield of alkenech1or hydrin is considerably impaired. This is prob- Al0 ably due to theformation of a CaClz-alkene chlorhydrin complex. With respect to thethird advantage, although a halohydrin-water constant boiling mixturefree from acid may be fractionated from a dilute, acid halohydrinsolution, l5'

I have found this method uneconomical when applied to batch methods,sin`ce under these conditions a small percentage-of the halohydrin ishydrolyzed. When it is .considered that the original concentration ofhalohydrin is usually about 2d 6%, it is seen that even'very smallamounts of hydrolysis have an appreciable eil'ect upon the yield. Forexample, I have found 'that from 2 to 5% of ethylene chlorhydrin is lostthroughthis cause on batch distillation. When operating in a 25continuous manner, on the other' hand, I have found that the loss due tohydrolysis is reduced to a negligible amount.

With respect to the use of an entrainer for the azeotropic removal ofwater,.I have r`found that o the maximum heat eiiiciency is ynotrealized by rst fractionating the dilute solution to obtain thehalohydrin-water constant boiling mixture, adding an entrainer theretoand subsequently re moving all the water therefrom in a seconddistillation. Likewise, it is grossly uneconomical to add the entrainerdirectly to the vdilute solution whereby the concentration isaccomplished in one operation. In the preferred embodiment of myinvention, I first fractionate the dilute aqueous halohydrin solution totake off a top product conl v siderably more concentrated in halogenthan the original solution, but containing appreciably less halohydrinthan the corresponding halohydx'inwater azeotrope. The optimumconcentration of 45 the distillate is dependent upon the halohydrin inquestion-and Vupon lthe entraining agent used in the following step.When using benzene as an 1 entraining agent in the concentration ofethylene chlorhydrin solution, I have found the optimum rconcentrationin the distillate from the ilrst fractionation` to be about 38% ethylenechlorhydrin. This mode of operation not only accomplishes aconsiderable` saving of ,heat when in conjunction with the followingsteps, but also is to a good measure responsible for the effectivenessof operating with the acid solution, When operating under theseconditions, it is found that the time tinuously, results in aconsiderable saving of heat.

In a second fractionating column wherein water is removed with the aidof a suitable entrainer, I accomplish the further concentration of thehalohydrin solution. According to this method of operation, I mayrecover nal concentrations of halohydrin ranging from slightly above theconcentration of the halohydrin-water constant boiling mixture up toabout 90%v halohydrin. If it is endeavored to produce still higherconcentrations, it is found that the product is contaminated with theentraining 'agent and consequently must be subjected to a furtherfractionation treatment to remove the same. In the concentration of'ethylene chlorhydrin solution, I nd it most economical to produce asolution containing from 50 to 60% chlorhydrln.

In order that my invention may be better understood, reference may behad to Fig. I illustrating schematically a suitable assembly ofapparatus by means of which the process may be carried out. I representsa storage tank containing the dilute aqueous halohydrin solution.

If it is preferable, for any reason, toforfeit the economy aifordedbythe .use of an acid solution and either partially or completelyneutralize'the solution previous to fractionation, this tank may, ifdesired, be equipped with suitable agitating means, inlet forintroducing the neutralizing agent, etc. The dilute aqueous, preferablyacid, halohydrin solution is caused to iiow continually viaa pipe 2 intoa suitable fractionating apparatus 3 being introduced into the columnthereof, preferably at the correct position as calculated by the wellknown methods. If desired, the solution may be preheated before enteringthe fractionating apparatus 3 or it may be introduced as a saturatedvapor. The required amount of heat is supplied to the fractionatingapparatus by any of the suitable conventional methods, such as bya'closed hot coil 4. 'I'he aqueous solution from which the halohydrinhas been substantially removed issues via a pipe 5. In the concentrationof ethylene chlorhydrin, for example, this lean solution, contains lessthan 1% of ethylene chlorhydrin. 'Ihe actual percentage of exithalohydrin, affording the most economical process, is, however,dependent upon the cost of thermal units and the value of the productand should be regulated within 'very narrow limits. The overheaddistillate from fractionating apparatus 3 containing a concentration ofhalohydrin appreciably lower than the halohydrin-water constant boilingmixture is passed continuously as a saturated vapor via a pipe 6directly into a second fractionating apparatus 'I being likewiseintroduced at a suitable point in the column. The necessary heat is.supplied to the apparatus -1 by a conventionalmeans such as a hot coil8. The iinal concentrated aqueous halohydrin solution issues via a pipeI3. The overhead product from fractionating apparatus 1 consisting of amixture of entraining agent, water and halohydrin passes continually viaa pipe 9 to a suitable condenser Il and thence to a suitable separatorlvessel II wherein the aqueous and hydrovia a pipe I4. In Fig. I the pipeI4 is arranged to convey the upper layer to fractionating apparatus 'land pipe I2 is arranged to convey the lower phase into pipe 2 by meansof which it is returned to fractionating apparatus 3. This arrangementis applicable when the hydrocarbonv phase is lighter than the aqueousphase and settles to the top. If, however, ethylene chloride or anyother material having a density greater than the aqueous phase, is usedas an entrainer, it will collect in separator II as the lower phase andin such case the vertical relation of the outlets to I2 and I4 must bereversed. If desired, the hydrocarbon from separator II may be rstv'aporized before being introduced at a suitable point intofractionating apparatus 1. To accomplish this a suitable vaporizer maybe inserted into line I4.

As an entrainer, I may use benzene, parain hydrocarbons or petroleumfractions boiling below 110 C., cycloparaflins boiling below 110 C.,ethylene dichloride, isopropyl ether, mixed ethers such as methyltertiary butyl ether, and the like. The requirements of a suitableentrainer are: it must form a minimum boiling mixture with water; itmust be relatively immiscible with Water; it must distill with water ata temperature appreciably lower than the boiling point of the halohydrinin question; it must not react chemically with the halohydrin and itmust be stable at its boiling point. While I may use any compound ormixture of compounds satisfying these requirements, I prefer to usebenzene as an entrainer When concentrating ethylene chlorhydrin, sincein thls'combination the least amount of heat is required to removeagiven quantity of water.

Whilethe present invention is applicable to the concentration lof any ofthe lower alkene halohydrins, I find it particularly suited for theproduction of ethylene halohydrin, and most particularly for theproduction of. solutions containing from about 42.5% to vabout by weightof ethylene chlorhydrin. It is obviously immaterial from what source thehalohydrin is derived. The invention is applicable to the concentrationof neutral or acid aqueous halohydrin solutions ranging from about 1%halohydrin up to the concentration of the halohydrin-water azeotrope.The maximum advantage is realized, however, in the concentration ofrelatively weak solutions, as for example,l solutions having aconcentration of halohydrin of from 4 to 15%.

One specific instance of a suitable application of the present inventionin lwhich the heat consumption has Abeen determined is given in thefollowing example, which I submit solely-for the purpose of furtheringthe understanding and appreciation of my invention. The sisted and wasarranged' essentially as shown schematically in Fig. I, to which ligurethe reference numbers refer.

Example An aqueous 6% solution of ethylene chlorhydrin container in atank I was fed continually at apparatus cona constant rate to anintermediate portion of a fractionating column 3 via a pipe 2. The spentdischarge issued from the bottom oi' the column (pipe 5) at atemperature of about 101 C. and contained 0.7% ethylene chlorhydrin. Thevaporous ethylene chlorhydrin-water mixture taken overhead in column 3and containing from 38 to 39% ethylene chlorhydrin, passed at atemperature of about 97 C. via a pipe 6 into the center of a secondfractionation column 1. The discharged product fromthe second columnissued continually via a pipe I3 at a temperature of about 98 C., andcontained 51.1% ethylene chlorhydrin. The overhead product from thesecond still 'I consisting of 91.6% benzene, '7.9% water and 0.5%ethylene chlorhydrin at a temperature of about '11 C. was passed'through a condenser I0 and the condensed distillate collected inaseparator ll. -The lower aqueous layer from the separator was returnedto the rst column 3 and the" upper hydrocarbon layer was returned to thetop ofthe second lcolumn essentially as described. The total heat ofvaporization required to effect the concentration from the original 6%solution to the final 51.1% solution was only about 1010 kg. Cal per kg.intake of the 6% solution and the yield was 89.5%.

It will be seen from the foregoing that the.

thermal economies realizable through the use of the present inventionresult from a novel combination of steps executed in a novel manner,which novelty is dependent upon the continuous method of execution.

I claim as my invention:

1. A process for the production of an aqueous solution of an alkenehalohydrin having a halohydrin concentration greater than in therespective halohydrin-water azeotrope which comprises the steps ofintroducing a dilute, aqueous, alkene halohydrin solution in aJcontinuous manner into 2. A process for the production of an aqueoussolution of an alkene halohydrin having a halohydrin concentrationgreater than in the respective halohydrin-water azeotrope whichcomprises the steps of introducing a dilute, aqueous, alkene halohydrinsolution in a continuous manner into a distillationapparatus,fractionally distilling 'said solution while maintaining a rate ofintroduction higher than that adapted to yield a halohydrin-waterazeotrope overhead fraction, thereby removing as anv uncondenseddistillate a more concentrated mixture of halohydrin, but containingless halohydrin than the respective halohydrin-water azeotrope,conducting said uncondensed distillate continually into a secondfractionating apparatus containing an entraining agent, andazetropically removing a portion of the water whereby a moreconcentrated aqueous solution of said alkene halohydrin is obtained. y

3. A process for the production of an aqueous solution of an alkenehalohydrin having a halohydrin concentration greater than the respectivehalohydrin-water azeotrope which comprises the steps oi. introducing adilute aqueous acidic alkene halohydrin solution in a continuous mannerinto a distillation zone, fractionally distilling said solution whilemaintaining arate of introduction and a temperature-higher than thatadapted to yield a halohydrin-water azeotrope overhead fraction, therebyremoving as an uncondensed distillate a more concentrated mixture ofhalohydrin, conducting said uncondenser distillate continually into asecond fractionating apparatus containing an entraining agent. andazeotropically removinga portion of the Water whereby a moreconcentrated aqueous solution of said aklene halohydrin is obtained.

4. A process for the production of an aqueous solution of an aklenehalohydrin having a halohydrin concentration greater than the respectivehalohydrin-water azeotrope which comprises the .steps of introducing adilute aqueous acidic alkene halohydrin solution in a continuous mannerinto a distillation zone, continuously and fractionally distilling saidsolution', maintaining said distillation zone at a temperature adaptedto remove as an uncondensed distillate a more concentrated mixture ofhalohydrin, said mixture containing les halohydrin than the respectivehalohydrinwater azeotrope, conducting said uncondensed distillatecontinually into a second fractionating apparatus containing anentraining agent, and azeotropically removing a portion of the waterwhereby a more `concentrated aqueous solution of said alkene halohydrinis obtained.

5. A process for the production of an aqueous solution of an alkenechlorhydrin having a chlorhydrin concentration greater than therespective chlorhydrin-water azeotrope which comprises the steps offractionally distilling a dilute, aqueous, alkene chlorhydrin solutionin a continuous manner while continuously introducing said dilutesolution into the distillation zone, maintaining '-'said rate ofintroduction and the temperature in the distillation zone above thatadapted to produce a chlorhydrin-water azeotrope, thereby removing as anuncondensed distillate a more concentrated mixture of chlorhydrin, saidmixture solution of said alkene chlorhydrin is obtained.

6. A process fo the production of an aqueous solution of an ethylenehalohydrin having a halohydrin concentration greater than in therespective ethylene halohydrin-water azeotrope which comprises the stepsof continuously introducing a dilute, aqueous ethylene halohydrinsolution in a continuous manner into a distillation apparatus,fractionally distilling said dilute solution while maintaining a rate ofintroduction a d a'temperature higher than that adapted to form therespective halohydrin-water azeotrope distillate, thereby removing as anuncondensed distillatel a more concentrated mixture of `halohydrin, saidmixture containing less halohydrin than the respective ethylenehalohydrin-water azeotrope, conducting said uncondensed distillatecontinually into a second fractionating apparatus containing anentraining agent, and azeotropically removing a portion of t e waterwhereby a more'concentrated aqueous so u tlon of said ethylenehalohydrin is obtained.

, 7. A process for the production of an aqueous solution of ethylenechlorhydrin having a chlor- 4A i hydrin concentration greater than inthe respective ethylene chlorhydrin-water azeotrope (42%) whichcomprises the steps of fractionally ldisf tilling a dilute, aqueousethylene chlorhydrin training agent, and azeotropically removing aportion of the Water whereby a product containing netween lr2.5 and 90%ethy1ene chlorhydrin is obtained.

8. A process for the production of an aqueous solution of ethylenechlorhydrin having a chlorhydrin concentrationbetween 42.5 and 90% whichcomprises the steps of continually conveyingan aqueous solution ofethylene chlorhydrin contain` ing between 4 and 15%- ethylenechlorhydrin into a distillation zone, fractionally distillingl saidaqueous ethylene chlorhydrin solution maintaining the rate ofintroduction into said distillation zone andthe temperature thereinhigher than that -adapted to yield an` ethylene ehlorhydrin-I waterazeotrope overhead, thereby removing as an uncondensed distillate avaporous mixture of ethylene chlorhydrinl and water containing be tween38 and 39% ethylene chlorhydrin, conducting said uncondensed distillateinto a second fractionating apparatus containing benzene as anentraining agent, and azeotropically removing a portion of the Waterwhereby a product containing between -42.5 and 90% of ethylenechlorhydrin is obtained.

9. A process for the production of aniaqueous ethylene chlorhydrinsolution having a chlorhydrin concentration greater than intherespective ethylene chlorhydrin-water azeotrope from aque# ousethylene chlorhydrin solutions containing between about 4% and 15% ofethylene chlorhy-v drin, which comprises continuously lintroducing' saiddilute aqueous chlorhydrin solution into a distillation zone,maintaining temperature conditions in said distillation zone whereby anethylene chlorhydrin-water mixture containing less chlorhydrin than therespective ethylene chlorhydrin-water azeotrope is continuouslyvaporized at a temperature of about 97 C., continuously withdrawing saidvapor mixture from said distillation zone, conducting said vaporous'mixture, without any previous condensation thereof, into a secondfractionating zone containing benzene as an entraining agent, andazeotropically distiliing a benzene-water mixture, whereby a portion ofthe water distilled from the rst distillation zone is removed andwhereby a yproduct containing more than 42.5% ethylene chlorhydrin isobtained.

WILHELM CAREL BREZESINSKA SMI'I'HUYSEN.

